I like cell phones. When he started tailgating and following your lane changes, I would recommend a quick call to 911 reporting the road rage. Mesa AZ PD, in my experience reacts very quickly to this type incident.

Much like a firearms incident, he who calls first generally gets the benefit of the doubt.

If the guy was driving erratically I would have reported the incident as a possible DUI. cops tend to respond quickly to those reports.